On Thu, Nov 22, 2018 at 09:27:02PM +0200, Igor Stoppa wrote: > I have studied the code involved with Nadav's patchset. > I am perplexed about these sentences you wrote. > > More to the point (to the best of my understanding): > > poking_init() > ------------- > 1. it gets one random poking address and ensures to have at least 2 > consecutive PTEs from the same PMD > 2. it then proceeds to map/unmap an address from the first of the 2 > consecutive PTEs, so that, later on, there will be no need to > allocate pages, which might fail, if poking from atomic context. > 3. at this point, the page tables are populated, for the address that > was obtained at point 1, and this is ok, because the address is fixed > > write_rare > ---------- > 4. it can happen on any available core / thread at any time, therefore > each of them needs a different address No? Each CPU has its own CR3 (eg each CPU might be running a different user task). If you have _one_ address for each allocation, it may or may not be mapped on other CPUs at the same time -- you simply don't care. The writable address can even be a simple formula to calculate from the read-only address, you don't have to allocate an address in the writable mapping space.
